Formatting duration object with decimal value

**Describe the bug**
Formatting a decimal value doesnt seperate out the hours and minutes
```
myDuration = dayjs.duration({ hours: 4.8 })
myDuration.format("HH:mm") => 4.8:undefined
```
**Expected behavior**
```
myDuration.format("HH:mm") => 04:48
```

The $ms is recorded correctly as `$ms: 17280000` and the following outputs correctly:
```
dayjs.duration(17280000).format("HH:mm") => 04:48
```
Am I expected to break up the duration into respected hours and minutes before passing it to dayjs duration?

**Information**
- Day.js Version [1.10.7]
- OS: [Ubuntu 20.04]
- Browser [chrome 94.]

Start by reproducing the dayjs.duration({ hours: 4.8 }).format("HH:mm") example and compare it with formatting dayjs.duration(17280000). The issue is done when the decimal-hour input produces 04:48, matching the expected output without manually splitting the duration.

Written by the indexing model from the issue text.